DSP56321TSLASHD datasheet(28/88 Pages) NXP

28 / 88 page

2-4

AC Electrical Characteristics

2.5 AC Electrical Characteristics

The timing waveforms shown in the AC electrical characteristics section are tested with a VIL maximum

of 0.3 V and a VIH minimum of 2.4 V for all pins except EXTAL, which is tested using the input levels

shown in Note 6 of the previous table. AC timing specifications, which are referenced to a device input

signal, are measured in production with respect to the 50 percent point of the respective input signal’s

transition. DSP56321T output levels are measured with the production test machine VOL and VOH

reference levels set at 0.4 V and 2.4 V, respectively.

Note:

Although the minimum value for the frequency of EXTAL is 0 MHz, the device AC test

conditions are 15 MHz and rated speed.

2.5.1

Internal Clocks

2.5.2

External Clock Operation

The DSP56321T system clock is derived from the on-chip oscillator or is externally supplied. To use the

on-chip oscillator, connect a crystal and associated resistor/capacitor components to EXTAL and XTAL;

an example is shown in Figure 2-1.

Table 2-4. Internal Clocks

Characteristics

Symbol

Expression

Min

Typ

Max

Internal operating frequency

•

With DPLL disabled

•

With DPLL enabled

—

Ef/2

(Ef

× MF)/(PDF × DF)

—

Internal clock cycle time

•

With DPLL disabled

•

With DPLL enabled

—

× ET

ETC × PDF × DF/MF

—

Internal clock high period

•

With DPLL disabled

•

With DPLL enabled

—

0.49

× T

ETC

—

0.51

× T

Internal clock low period

•

With DPLL disabled

•

With DPLL enabled

—

0.49

× T

ETC

—

0.51

× T

Note:

Ef = External frequency; MF = Multiplication Factor = MFI + MFN/MFD; PDF = Predivision Factor;

DF = Division Factor; TC = Internal clock cycle; ETC = External clock cycle; TH = Internal clock high;

TL = Internal clock low

Figure 2-1. Crystal Oscillator Circuits

Suggested Component Values:

fOSC = 16–32 MHz

R = 1 M

Ω ± 10%

C = 10 pF

± 10%

Calculations are for a 16–32 MHz crystal with the following parameters:

•

shunt capacitance (C0) of 5.2–7.3 pF,

•

series resistance of 5–15

Ω, and

•

drive level of 2 mW.

XTAL1

Fundamental Frequency

Crystal Oscillator

XTAL

EXTAL

Note: Make sure that in the PCTL Register:

•

XTLD (bit 2) = 0

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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